The invention relates to a method of testing a network setup with a plurality of data generators, the data of which is to be transmitted and received among the data generators over a data path and which is to be processed by control units, priority criteria being established for the competing transfer of the data on the data path.
Such networks serve to make possible data communication between a multiplicity of computers, in particular controllers or microprocessors. In principle, in these cases each computer can receive and evaluate the data of the other computers and thereupon, if appropriate, generate new data itself. Due to the networking of the computers brought about by means of the data bus, competing states of data-transmit readiness arise, for the processing of which priority criteria are established in a protocol. If a computer at transmit readiness has to wait for a priority transmission request, the computer must defer its transmission request according to the respective protocol; with some protocols, it is necessary to switch over immediately to "receive" in order to be able to receive and, if appropriate, evaluate the data transmission with higher priority if the data transmission is intended for it.
For the design of such a network, the bandwidth of the data paths, for example a data bus, and thus the transfer rate attainable on the data path, are essential design criterion. For reasons of expense, the bandwidth should be kept as small as possible, whereas a fast data transfer requires a large bandwidth.
Thus far, the designer of these networks has no readily available aids for designing such a network. The designer is therefore reliant upon empirical values. As there is still relatively little experience available thus far, and the parameters of a network are disparate, by definition, complex and cannot be interwoven in an analytically unique manner, the network will have to be set up before it can be determined whether or not it operates in the desired way. However, at this time, this determination can only take place with respect to the macroscopic result. Thus, for example, with a network used in an automobile, the determination is made by the function the automobile which is controlled by the network. In this case, it can be determined whether the coordination, for example of a braking operation with other functions of the network control operate satisfactorily. If considerable response delays, which are attributable to a permanent or situation related overloading of the data path, are found in such cases, the entire network must be replanned and reconstructed. Setting up a network which operates in a usable manner is therefore expensive and time-consuming.
For the analysis of a completely set up network, recourse can be made, if appropriate, to logic analyzers, which can store and display on a screen the signal level progression, for example the signal applied at an interface. With a relatively complex data transfer, there are then a multiplicity of photographically recorded signal progressions available, the examination of/which is time-consuming and laborious and requires a high degree of concentration over a long period on the part of the person examining them. Such devices are, in some circumstances, also capable of transmitting certain test signals via an interface or the like in order to verify satisfactory transfer or to determine faults. These known devices are not, however, suitable aids for network planning.